I wrote about being first or second: here.
I should clarify what I meant. When you are in a race, its better to be first (ie, I bet that the first person who walked on the moon got most of the glory, etc.). But I meant that sometimes one paper has an idea and it does not catch on. The second paper that has that idea might use it in a slightly different way, but it's the second paper that seems to get the cites. Sometimes the papers are years apart.
There is an obvious statistical problem with this—I remember such cases because the second paper shows up in print in a good journal, meaning that the work passed some sort of hurdle. Many other 'second papers' probably never make it to a top journal anyway.
I am still puzzled, though.